Process of forming electrical connectors

ABSTRACT

Electrical connector or terminal lugs are provided by using bending, stretching and drawing techniques rather than cold flow methods. To fabricate the terminal lugs, a flat piece of aluminum or copper is first formed as a cup by drawing techniques. Then, the closed end of the cup is sheared free, flattened and wedged within the walls of the cup. Afterward, suitable holes are punched or drilled to accept wires, or cables, and fasteners. The resulting terminal lugs may be used in fastening wires or cable to bus bars.

United States Patent McLaughlin et al.

[451 Mar. 21, 1972 PROCESS OF FORMING ELECTRICAL CONNECTORS Inventors:Bernard John McLaughlin, St. Louis; Arthur Louis Colvis, Hazelwood, bothof Mo.

International Telephone and Telegraph Corporation, New York, N.Y.

Filed: Oct. 31, 1969 Appl. No.: 872,918

Assignee:

US. Cl. ..29/629, 29/630 R, 113/119, 339/272 R, 339/263 R,.339/277 RInt. Cl. ..H02g 15/00, HOlr 9/00 Field ofSearch ..29/630R; 1 13/1 19;339/272, 339/263, 277

References Cited UNITED STATES PATENTS 1/1911 Hector.;.'.'.'.;...339/2'"7 2 2,185,981 1/1940 l-luller ..29/630X 2,223,85312/1940 Mebold ..29/630 Primary Examiner-John F. Campbell AssistantExaminerRobert W. Church Attorney-C. Cornell Remsen, Jr., Walter J.Baum, Percy P. Lantzy, J. Warren Whitesell, Delbert P. Warner and JamesB. Raden [57] ABSTRACT 6 Claims, 23 Drawing Figures PATENTEDMARZI I9723.650.025

sum 2 or 4 FIG. .9

FIG. /0

PATENTEDMARZI I972 SHEET 3 OF 4 PATENTEDMARZI x912 SHEET h 0F 4 FIG. 18

PROCESS OF FORMING ELECTRICAL CONNECTORS This invention relates to wireconnectors and their fabrication and particularly to connectors in theform of terminal lugs made of copper or aluminum.

Terminal lugs are normally used to fasten essentially round (solid orstranded) wires to bus bars having flat surfaces. The optimum materialfor terminal lugs is pure copper when such factors as cost, ductibilityand conductivity are considered.

Small terminal lugs are normally made of copper and are normally coldforged. In this way, the high conductivity and ductibility of copper areused advantageously and the superior strength of cold worked material isavailable. In the past, however, large sized terminal lugs have not beencold forged because of the great compressive forces that are required tocause cold flow of the large quantity of material involved. The cost ofmachinery and dies capable of withstanding the extreme pressuresrequired have always made this method uneconomical. Because of this,large lugs are usually made by casting bronze material. The conductivityof bronze is much less than that of copper. The bronze lugs, therefore,have inferior electrical characteristics when compared to copper lugs.

It is an object of the present invention to provide for improvements inlarge terminal lugs. It is a further object to improve the fabricationof large terminal lugs and similar articles from flat strip stock ofpure copper or aluminum. Certain aspects of the invention involve theuse of bending, stretching and drawing techniques, rather than cold flowmethods. These techniques require far less force than cold forging andtherefore the tooling and machinery are more economical.

The foregoing objects and others ancillary thereto are preferablyrealized by drawing part of a flat strip of metal in successive stagesinto a cup while another portion is left flat. The flat portion formsthe tang of the lug. The bottom of the unformed portion of the cup isthen formed to a spherical curvature. At this same time, the edge of theopening at the other end of the cup, where the transition from cup toflat tang occurs, is formed as a seat which may be a circular ledge, acrimp ring, or a ledge made up ofa number oflands. In this way, thediameter of the hole at the tang end of the cup is defined by the seatand is made smaller than the internal diameter of the cup. Thespherically curved bottom portion is then sheared free and punched downinto the interior of the cup to lodge against the seat where it isflattened and wedged within the walls of the cup. Holes are thenpunched, or drilled, vertically through the cup near the closed end toreceive wires or cables. The open end of the cup is prepared, e.g., bycutting threads, so that a plug may be inserted to hold the wire orcable in place. A suitable hole may be drilled in the tang to produce afinished terminal lug of use in fastening wires and cable to bus bars.

All of the steps referred to in the preceding paragraph may be preformedserially in a multistation progressive die. The part is carried fromstation to station by means of a scrap train. This method requires aminimum of direct labor cost.

The above mentioned and other features and objects of this invention andthe manner of obtaining them will become more apparent, and theinvention itself will be best understood by reference to the followingdescription of an embodiment of the invention taken in conjunction withthe accompanying drawings, in which:

FIG. 1 illustrates a flattened piece of copper or aluminum pre-shapedfor use in the practice of the invention,

FIG. 2 is a perspective view showing a cup formed from the strip ofmetal ofFlG. 1,

FIGS. 3 and 4 are perspective views showing the cup at further stages offormation and more clearly showing the tang as well,

FIGS. 5 and 6 are perspective views in which FIG. 5 shows the lugfollowing removal of the closed end and FIG. 6 shows how holes areplaced in the tang and through the main body of the lug,

FIGS. 7A and 7B illustrate respectively a threaded plug and a piece ofbare wire which are shown assembled with the lug in FIG. 7C,

FIGS. 8-11 are cross sectional views of a cup as it would be formed infour draw stages according to the invention,

FIG. 12 is a sectional view showing the effects of additionalmanufacturing stages in which the flange has been set and the closed endof the cup has been formed to a spherical curvature,

FIG. 13 is a sectional view of an embodiment of a terminal lug using theconfiguration of FIG. 12,

FIGS. 14A and 14B illustrate, in cross section and in a top viewrespectively, the effect of broaching a barrier shelf formed by threelands at the open end of the cup,

FIG. 15 shows in cross section the result of piercing the closed end ofthe cup to form a slug, flattening the slug and forming it against thebarrier shelf,

FIG. 16 illustrates in cross section a combination of dies and punchesused in forming the cup,

FIG. 17 illustrates, in partial section, a further stage in theformation of a cup,

FIG. 18 illustrates, in partial section, an anvil and a punch being usedin shaping a terminal lug,

FIG. 19 shows in partial section a variation in the method for forming aterminal lug, and

FIG. 20 shows in partial section a further stage of the variationillustrated in FIG. 19.

Turning now to FIGS. 1-4 there are illustrated various stages of anexemplary series of steps involving drawing the original flat piece 1 ofFIG. 1 through the stages of FIGS. 2 and 3 (plus additional drawingsteps, if necessary) to form the cup 2 having a closed end at 3 and atang 4, as shown in FIG. 4. FIG. 5 illustrates the results of a stepfollowing formation of the cup 2 of FIG. 5 in which the end 3 of the cup2 of FIG. 4 has been punched out and pressed into and through the cup toseal the other end of the cup (not shown). FIG. 6 illustrates a furtherstage in which the interior of the lug has been prepared to receive aslug and a countersunk hole 6 has been made in the tang 4.

After the lug has been prepared to the extent illustrated in FIG. 5, itis finished as in FIG. 6. The tang 4 is pierced and countersunk as at 6in FIG. 6. Holes are pierced through the cup 2 at 8 and threads 5 areapplied to the interior of the lug. In the form shown in FIG. 6, the lugcan receive a bare wire as at 10 (FIG. 78) through the holes 8. The wirecan then be fastened in place by a threaded plug 12 (FIG. 7A) to producean assembly as in FIG. 7C.

A variety of procedures for drawing flat piece 1 of FIG. 1 through aseries of stages to produce a terminal lug having the degree ofcompletion shown in FIG. 5 are illustrated further in the drawings inFIGS. 8-20. A first series of four drawing stages are shown in FIGS.8-11 in which a series of punches and dies (not illustrated) ofsuccessively smaller size are used to draw a cup down to the form shownin FIG. 11. References may be made to the Metals Handbook" 8th edition,Vol. 1, published by American Society for Metals, Novelty, Ohio, andparticularly to pages 709-717 for further details relating to theformation of cup shaped metal parts by the use of deep drawing dies in apress.

FIG. 12 illustrates in cross section the result of applying suitablepunch and die operations to a cup formed like that shown in FIG. 11. Itshould be noted particularly that the end 3 of the cup has been reformedto a spherical curvature or Belleville top now labeled 3 and that a moredefinite and limited bend exists at 9 while the flange 4 and tang 4 areset.

The configuration indicated in cross section in FIG. 12 can be used tofashion a lug as shown in FIG. 13. In FIG. 13 a stranded wire at 10 ispassed through holes at 8 punched through the cup. The wire 10 is heldin place in the cup by a threaded plug or clamp screw 12.

FIGS. 14A and 148 show respectively in cross section and in elevationthe results of broaching the lower barrier shelf to form a seat for aslug in the form of three lands L. Broaching may be performed with asuitable die and anvil as shown in detail elsewhere in thisspecification. FIG. shows in cross section the effect of piercing theclosed end 3 of the cup (as shown in FIG. 14A) to form a slug andflattening the slug as shown at 3", with a suitable flat punch Pl,against the lands L and an anvil at A1.

FIG. 16 illustrates a different procedure for further shaping a cup suchas that shown in FIG. 12. In this embodiment of the invention a cup 2 isplaced in a pair of dies D1 and D2 and punches P2 and P3 are positioned.Pressure is then applied to the dies and punches to shape the cup asshown in cross section. By this procedure the cup 2 is shortened whenthe metal at is extruded upward to form a ridgelike ring.

FIG. 17 illustrates a manufacturing step in which the vertical circularprotrusion or ridge at 20 (FIG. 16) is depressed or turned over by apunch P4 to form a seat for a slug in the form of a crimp ring at 21.The crimp ring 21 may be said to serve as a floor, a ledge or a seat forthe slug 3" which is pierced at the same time by the punch P5. In FIG.18, the punch P5 is shown to have pierced the curved closed end 3forming the slug 3" and forcing it against an anvil A2 and against thecrimp ring 21.

FIGS. 19 and 20 illustrate an additional way of forming a lug inaccordance with the invention. In this instance, the cup 2 is pierced atits closed end 3' by a punch at P6 and pushed through the cup to abutagainst an anvil at A3 and against a ledge at L2 formed by action of theanvil A3 against the cup 2 and the die at D3.

We claim:

1. A method for forming a terminal lug comprising forming a cup bydrawing a portion of a flat metallic piece in a series of steps,

shaping the closed end of the cup by imparting a curvature to each faceof the end,

forming a ledge at the open end of the cup,

shearing free the closed end of the cup to form a slug,

punching the slug through the interior of the cup and into contact withthe ledge, and flattening the slug into the open end of the cup to wedgeit firmly within the walls of the cup and against the ledge. 2. A methodfor forming a terminal lug as claimed in claim 1 in which the method forforming a ledge includes breaching a plurality of lands to serve as saidledge. 3. A method for forming a terminal lug as claimed in claim 1 inwhich the step of shearing free the closed end of the cup to form a slugincludes piercing the closed end with a die, and the step of punchingthe slug through the interior of the cup and into contact with the ledgeincludes flattening the slug against an anvil at the same time it isflattened against the ledge. 4. A method for forming a terminal lug asclaimed in claim 1, in which the method for forming a ledge at the openend of the cup includes forming a ridgelike ring by subjecting the cupto pressure along its central axis and punching the ridgelike ring toturn it over and form a crimp ring to serve as the ledge. 5. A methodfor forming a terminal lug as claimed in claim 1, in which the methodfor flattening the slug to wedge it within the walls of the cup andagainst the ledge includes the application of force to the slug betweenan anvil on one side of the ledge and a punch on the other side of theledge. 6. A method for forming a terminal lug as claimed in claim 1, inwhich the method for forming a ledge comprises:

placing the cup within the cradle of a die, and applying force on ananvil at the open end of the cup to form the ledge against the die.

1. A method for forming a terminal lug comprising forming a cup bydrawing a portion of a flat metallic piece in a series of steps, shapingthe closed end of the cup by imparting a curvature to each face of theend, forming a ledge at the open end of the cup, shearing free theclosed end of the cup to form a slug, punching the slug through theinterior of the cup and into contact with the ledge, and flattening theslug into the open end of the cup to wedge it firmly within the walls ofthe cup and against the ledge.
 2. A method for forming a terminal lug asclaimed in claim 1, in which the method for forming a ledge includesbroaching a plurality of lands to serve as said ledge.
 3. A method forforming a terminal lug as claimed in claim 1, in which the step ofshearIng free the closed end of the cup to form a slug includes piercingthe closed end with a die, and the step of punching the slug through theinterior of the cup and into contact with the ledge includes flatteningthe slug against an anvil at the same time it is flattened against theledge.
 4. A method for forming a terminal lug as claimed in claim 1, inwhich the method for forming a ledge at the open end of the cup includesforming a ridgelike ring by subjecting the cup to pressure along itscentral axis and punching the ridgelike ring to turn it over and form acrimp ring to serve as the ledge.
 5. A method for forming a terminal lugas claimed in claim 1, in which the method for flattening the slug towedge it within the walls of the cup and against the ledge includes theapplication of force to the slug between an anvil on one side of theledge and a punch on the other side of the ledge.
 6. A method forforming a terminal lug as claimed in claim 1, in which the method forforming a ledge comprises: placing the cup within the cradle of a die,and applying force on an anvil at the open end of the cup to form theledge against the die.